Help with brake problems

[black95]

Alright guys, I'm at the end of my rope on my rear brakes. This is my last ditch effort for help.

Here's the background: I've got a '95 4runner, SAS, V6 front calipers, FJ60 rotors. 7 years ago, I swapped in a chevy vortec 4.3, when doing that swap, I had to lose the anti lock brake -- whatever it was on the front passenger frame rail. Ever since then, no rear brakes.

Replumbed the system without the anti lock box, straight off the rear port of the master cylinder (closest to the firewall). Swapped out the master cylinder, no luck. Swapped to FJ80 master cylinder, still, no luck. Ditched the LSPV completely, still, no rear brakes. Plumbed a whole new line straight down off the master right to the rear brakes, only a few bends -- yup, no rear brakes, at all, none, what-so-ever.

Used to live in Louisiana, so this was not too much of a big deal. Now I'm in Colorado snow country and it sucks bad. Front brakes lock up almost uselessly in the ice with no stoppage of the rear at all, and in 2 wheel drive, the rear will sit there and spin at stop lights, no matter how hard you are on the pedal. I know the rear brakes are put together right, and the e-brake functions perfectly.


I give up, any ideas??? Anything??? I've been dealing with this for 7 YEARS...
I remember the front and rear brakes used to be tied together somehow, I was going to go that route next. Also wondering if there is something special about the rear drum's wheel cylinder, maybe it's a larger size and not getting enough fluid?

 

[bcstoy]

Alright guys, I'm at the end of my rope on my rear brakes. This is my last ditch effort for help.

Here's the background: I've got a '95 4runner, SAS, V6 front calipers, FJ60 rotors. 7 years ago, I swapped in a chevy vortec 4.3, when doing that swap, I had to lose the anti lock brake -- whatever it was on the front passenger frame rail. Ever since then, no rear brakes.

Replumbed the system without the anti lock box, straight off the rear port of the master cylinder (closest to the firewall). Swapped out the master cylinder, no luck. Swapped to FJ80 master cylinder, still, no luck. Ditched the LSPV completely, still, no rear brakes. Plumbed a whole new line straight down off the master right to the rear brakes, only a few bends -- yup, no rear brakes, at all, none, what-so-ever.

Used to live in Louisiana, so this was not too much of a big deal. Now I'm in Colorado snow country and it sucks bad. Front brakes lock up almost uselessly in the ice with no stoppage of the rear at all, and in 2 wheel drive, the rear will sit there and spin at stop lights, no matter how hard you are on the pedal. I know the rear brakes are put together right, and the e-brake functions perfectly.


I give up, any ideas??? Anything??? I've been dealing with this for 7 YEARS...
I remember the front and rear brakes used to be tied together somehow, I was going to go that route next. Also wondering if there is something special about the rear drum's wheel cylinder, maybe it's a larger size and not getting enough fluid?

You actually do not mention how you have done the work. You know you have to bench bleed the MC first, then bleed the wheels in the right sequence. Also there is a posibility that your proportioning valve is deffective too.

 

[black95]

All the master cylinders were bench bled. The system was bled correctly, starting with the wheel farthest away from the master cylinder. No proportioning valve in the system, no LSPV (Load Sensing Proportioning Valve).

Oh yeah, and the system is leak free, pedal is tight.

So either, the master cylinder in a second gen 4runner (and FJ80) is not designed to use to rear brake port without the help of the power steering pump driven anti lock booster, or there is something about the rear wheel cylinders. I think my next move is going to be to an FJ60 master, since they hadn't thought of the PITA anti lock systems yet.

 

[black95]

Anyone running a second gen 1" bore master in their early mini truck? I seem to remember that was a popular swap to upgrade from the smaller bore master. That would rule out my thought of the second gen master not using the rear port without the booster.

 

[pappy]

Anyone running a second gen 1" bore master in their early mini truck? I seem to remember that was a popular swap to upgrade from the smaller bore master. That would rule out my thought of the second gen master not using the rear port without the booster.

Yep. 1" mini-truck master in my 1985, to stock rear drums via LSPV, to V6 calipers. No issues. Luv it.

Also, 1" FZJ80 master in my FJ40, to V6 calipers in front, Chebby disk conversion in back via manual proportion valve. No issues. Scary stopping power.

 

[pappy]

Are able to bleed the back? Are you pushing fluid? Wondering if you might have an issue with the wheel cylinders, or rear brakes not assembled correctly. If you are hard plumbed to the rear they should be working harder than the fronts without a proportion valve (LSPV).

 

[black95]

Are able to bleed the back? Are you pushing fluid? Wondering if you might have an issue with the wheel cylinders, or rear brakes not assembled correctly. If you are hard plumbed to the rear they should be working harder than the fronts without a proportion valve (LSPV).

Exactly, and yet, I get nothing.

Yes, the rears are bleeding, and fluid runs out on it's own if the bleeders are left open. The rear brakes are for sure 100% assembled correct, and adjusted.

I looked at my '88 truck's system, and it's curious to me that the front and rear systems are tied together. This suggests to me that A) the rear circuit of the master cylinder needs more pressure from the front B) that extra line is a fluid dump for the LSPV C) that second line balances the system.

My current system has the two front calipers straight off the front port, and one line off the rear to the junction block on the rear axle.


The 88's brake system...

 

[black95]

The 95's old ABS pump/ box/ thingy used to interrupt line A if I remember right, and the box used power steering pump pressure and lines to somehow pulse the rear brakes. That box used to have two lines to it, and I just bent a horseshoe in a line and reconnected everything, and got rid of those lines. That is where all this got started.

Regardless of what happens, I am not going to put the LSPV back in, I know too many trucks that have had problems/ leaks in them. So the question is, how to make the system work with an aftermarket proportional vavle, and only one line to the rear?

 

[Bogo]

That rear ABS controller should have no effect on braking if off or failed. Removing it from the circuit should also have no effect.

What happens if you pump the brakes?

 

[black95]

Just pulled the rear drums off (had to back off adjusters) and checked for movement, there is no shortage of that. My little 75 pound daughter pushed the pedal to the floor, and those pads move a lot, and the drum surfaces are shiny to show pad contact. Installed a Proportional valve and it makes no difference.

I'm starting to think about the front brakes now. There is no visible residual valve on the front. My thoughts as of now:

1) the rears are working, but don't have strength.

2) the fronts are not pulling away from the rotors for lack of residual valve and are working TOO well, or coming on too soon, or they are getting all the pressure through the master because the lines are not plumbed the way toyota intended.

Thoughts?

 

[black95]

What happens if you pump the brakes?

The pedal is solid, pumping them really does nothing because the system is tight. The pedal doesn't even push half way down and feels great. A member of the Rising Sun Denver forum seems to think I need a whole system proportioning valve instead of a single circuit type like I installed. This would require a complete re-plumb of the system. Suck.

 

[bcstoy]

The pedal is solid, pumping them really does nothing because the system is tight. The pedal doesn't even push half way down and feels great. A member of the Rising Sun Denver forum seems to think I need a whole system proportioning valve instead of a single circuit type like I installed. This would require a complete re-plumb of the system. Suck.

I am not sure I read your posting correctly but if you do not have a proportioning valve in the system you may never get the brakes to work right. Not having it also may affect the bleeding sequence. I have a 2wd nissan that does not use a the proportioning valve and it was a nightmare to get it to work. For that the bleeding sequence was rear DS- rear PS, front DS and front PS. In systems with no LSPV it is the MC that has it. In the worst scenario you may have to set it like your 88. It is not safe to have a system that does not include a LSPV. BTW the nissan with LSPV in the MC is on the 88 trukcs with one port in angle.

 

[black95]

It didn't work stock with a LSPV either. Which may mean the LSPV was bad, I'll never know because I threw it away. Those leaky, Pain in the @ss valves are junk, so I'm trying to figure out how to do this without one.

 

[bcstoy]

It didn't work stock with a LSPV either. Which may mean the LSPV was bad, I'll never know because I threw it away. Those leaky, Pain in the @ss valves are junk, so I'm trying to figure out how to do this without one.

I think you will still need one. You may want to try the Nissan MC I talked about it. That system does not have a separate LSPV and drove my crazy. Nissan uses both one with it and one without it. Like I said the MC is also a LSPV. A while back had a subaru that gave me lots of problems because of a leaking LSPV.

 

[85 t runner]

ive heard not sure if its true that the lspv is also to slow the presure down because the drum brakes dont need as much pressure to stop like the disk brakes do so if you remove the lspv when braking your rear drum brakes might be locking up or stopping first before the front